I didn't think it was necessary to mark man pages with %doc? (Same
for gtk-docs in /usr/share/gtk-doc/html for rpm in rawhide.)
build/files.c in rpm marks these as docs implicitly AFAICT. Is there
something I'm missing that you can clue me in to?

Yes, no need to mark man pages as %doc, they get the treatment
automatically. Although one should be using %{_mandir} for them, not
%{_datadir}/man/

And yes gtk-doc's are also automatically considered as %doc by rpm
4.4.2.1.